docs: def clear_output(output=None):
      '''
      Remove file targets in `_output` when a step fails to complete
      '''
      for target in env.sos_dict['_output'] if output is None else output:
          if isinstance(target, file_target) and target.exists():
              try:
                  target.unlink()
              except Exception as e:
                  env.logger.warning(f'Failed to remove {target}: {e}')